It is thought the kidnappers could have been posing as security personnel.

"Nobody knows where he is. They left his car behind, probably they thought it could be traced," a government source told the Associated Press.

The BBC's Rana Jawad in Tripoli says there has been a sharp increase in security threats against the cabinet since the government announced it was taking steps to disarm and disband the militias.

Last week, the prime minister's building was briefly surrounded by an armed group demanding his resignation, and on Sunday, the justice ministry was similarly surrounded for several hours.

The government is still struggling to consolidate its powers over the many militias which formed after the war that toppled Col Muammar Gaddafi.

But out correspondent says there is a widespread view amongst Libyans that their government has become seriously locked in a power struggle with militias trying to keep their influence on the streets of Libya.

BBC links

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.